The present invention relates generally to wheelchairs. More particularly, it concerns a drive system for wheelchairs that provides plural-speed, drive-wheel operation via hand wheels selectively operatively connected via a hub subsystem to the wheelchair's drive wheels.
Wheel chair drive systems are known that include plural-speed hub assemblies including toothed gears that provide speed changing and wheelchair propulsion via selective manual positioning of a speed change control handle and via oscillatory manual operation of a propulsion lever, flywheel and operatively connected drive wheels. Such drive systems obtain some mechanical advantage for the user who may lack upper body mobility and/or strength as well as providing lower speeds for uphill travel. Wheelchairs are known that provide hand wheels fixedly attached to corresponding drive wheels for manual rotary operation of the drive wheels via manual rotary operation of the hand wheels. Such direct-drive wheelchairs also provide some mechanical advantage, but require relatively great upper body mobility and strength especially when the traveled terrain is uphill and down.
The invented wheelchair drive system uniquely combines certain of the advantages of conventional drive systems by providing a plural-speed hub subsystem operatively connected between a wheelchair's hand wheels and corresponding drive wheels. By operatively interposing plural-speed hub subsystems between conventional rotatable hand wheels and their corresponding drive wheels, more natural rotary motion of the hand wheels propels the wheelchair by selectively engaging the drive wheels dependent upon a manually operated gear-shifting mechanism. Such greatly facilitates wheelchair operation by users of different strengths and facilitates wheelchair travel over uneven terrain.
Preferably, each of dual hub subsystems includes a hub body fixedly connected with easily accessible hub-rotator structure (i.e. a hand wheel) and with a corresponding drive wheel. Hub-coupling structure, preferably in the form of a hub spindle, is fixedly attached to the wheelchair and provides a coupling between it and a manually shiftable, plural-speed transmission substructure of the hub. Operator actuation of a hand wheel causes rotation of the hub about an axis defined by the spindle. The spindle is selectively drive wheel-connected by operation of the plural-speed transmission substructure.
The transmission substructure, also referred to herein as a gear train, preferably includes plural sets of planetary, sun and ring gears, with the sun gears mounted on the spindle, the ring gears formed along an inner surface of the hub body and the planetary gears positioned along a mounting member that is shiftable lengthwise in parallel with the spindle's central axis. The mounting member is spring-biased against a first side of the hub body, with the member being shiftable against the spring's tension into alternative positions by a shift rod that extends along a central void within the spindle. The shift rod is positionable by manual operation of a shift bar connected therewith that extends outwardly of the spindle and provides easy user access via a cable-connected shift lever. A clutch, an active brake, and/or a parking brake may be provided for smooth, at-speed shifting between plural speeds and stopping/parking when riding on difficult terrain or when the user fatigues.
These and additional objects and advantages of the present invention will be more readily understood after a consideration of the drawings and the detailed description of the preferred embodiment.